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Equipment Discussions >> Mounts

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neilson
professor emeritus


Reged: 08/22/10

Re: Why me? new [Re: TALK2KEV]
      #5401289 - 09/03/12 03:30 PM

Hi Kevin,
This is great, thanks for displaying some long guided images. I was hoping for better results, but at least I will lower my expectations when I get my 9.25ota tomorrow. My f/10 focal length will show problems much worse. But the reduced weight should show an improvement over my images with the 10" last week. The images I didn't show the other day were so much worse than the few I did post. And my mounts problems were in 2 directions. I'm guessing the guiding will make the problems much less and in one directions only. And the reduced weight should help also.
I will start at f/10 just to magnify the problems so I can see them easier. Then use a focal reducer later. Maybe Meade will come up with that PEC fix they promised soon and make things easier on us for imaging.
Good job Kevin and thanks for the images. And thanks for listing the settings you used in PHD they will be helpful.
neilson


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TALK2KEV
sage


Reged: 03/08/06

Loc: Oklahoma
Re: Why me? new [Re: neilson]
      #5401429 - 09/03/12 04:40 PM

PEC was off. I didn't use PEC because of its inconsistency.
The error you see is in RA its that same back and forth oscillation east to west that the mount always had. When using PHD and in tools you can put a grid up you can see the movement on screen its very small only the thickness of the grid line you will see the star on one side then on the other. I was thinking that if my mount was like Neilson dry with on grease maybe its getting hung up at some places and the give you see is the spring loaded worm gear releasing and grabing which its unpredictable causing the inconsistency seen in PEC?
Neilson did you have to grease both of your mounts?
I could try turning on PEC I was just wondering the spikes seen in training that wasn't consistent if PEC send corrections where none is needed that will cause a error which is why I didn't use PEC.

To give a small history on PEC training I did six training runs to compare the PEC graph on all six while a lot of the spikes matched up a few did not and this was in every run.
All the PEC training was done with Dec Correction turned off.


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TALK2KEV
sage


Reged: 03/08/06

Loc: Oklahoma
Re: Why me? new [Re: TALK2KEV]
      #5401474 - 09/03/12 05:00 PM Attachment (42 downloads)

Here is a 5min sub of m57 again at 430mm fl the full frame looks ok but when you get to actual pixel you can see the error

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TALK2KEV
sage


Reged: 03/08/06

Loc: Oklahoma
Re: Why me? new [Re: TALK2KEV]
      #5401475 - 09/03/12 05:01 PM Attachment (48 downloads)

here is actual pixel

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OzAndrewJ
scholastic sledgehammer
*****

Reged: 11/30/10

Re: Why me? new [Re: TALK2KEV]
      #5401508 - 09/03/12 05:24 PM

Gday Kev

Quote:

I could try turning on PEC




If you do, you will have to retrain it unless you have religously parked after each session since the last train. There is no way for the code to resynch the PEC model to the worm, so the first time you turn off without parking, your data gets desynched.

Quote:

I was just wondering the spikes seen in training that wasn't consistent




There is a difference between spikes and actual "non recurring" PE.
By spikes, i mean the severe spikes we saw in your first PEC run.
( And that David saw using PHD ). Cant explain that yet.
By non periodic PE, i mean effects generated by the geartrain.
As the gearbox has an oddball ratio of 53.5859375:1 ( 6859/128:1 )
it only truly resets itself every 128 turns of the worm.
Thus, if there is large PE in the gearbox, "relative" to the worm PE,
then the effects of the gearbox will start to show up,
and cannot be corrected by a single turn PEC model.
More data from a range of scopes is required here.


Andrew


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neilson
professor emeritus


Reged: 08/22/10

Re: Why me? new [Re: TALK2KEV]
      #5401554 - 09/03/12 05:54 PM Attachment (37 downloads)

Hi Kevin,
I only checked the grease in the second mount. There might be one way to tell. put it in polar and release the clutch. now with no ota or no weights or the the last 2 weight bars. it will be heavy upside down. now rocket it back and forth or spin it. if it moves real easy then it probably has grease but if you feel a slight drag or it doesn't spin and spin then you might not have grease. or it might just be tight.
After I put the grease it was so much easier to balance. It moved very easy. Before the grease it was hard to be sure it was balanced.
But I dont think that is your problem. Even after I greased mine it still rocking in RA. I am going to post one of the images made within a few minutes of those I posted last week. It goes forward then back then forward. At least thats what I think its doing. Its 95 seconds and I cropped and brightened it to show the smaller star in the upper left.
neilson


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TALK2KEV
sage


Reged: 03/08/06

Loc: Oklahoma
Re: Why me? new [Re: neilson]
      #5401613 - 09/03/12 06:27 PM

Andrew
I do park the scope after each session, but I will train the PEC again tonight and try to do some more long exposure. Did you ever look at the data set I sent you on the long unguided runs?
Thanks Andrew for all your help with the PEC. If you think of anything else to try let me know.

Neilson
My mount turns easily in RA it doesn't hang or get in a bind
it moves easy on both axis the photo above looks like mine to just longer FL. If I put a barlow on the scope I could get 860mm fl. I might try that but even though the Barlow is a televue 2" I'm sure the pics are not going to look as good .


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OzAndrewJ
scholastic sledgehammer
*****

Reged: 11/30/10

Re: Why me? new [Re: TALK2KEV]
      #5401646 - 09/03/12 06:47 PM

Gday Kevin

Quote:

Did you ever look at the data set I sent you on the long unguided runs?




Yep, but i dont know how to interpret them.
I can read the time, dx, dy values,
but i dont know what they really represent.
Also, i cant find a way to import a log into PHD
to redisplay it so i can cross reference anything.
Will try some different things today, but currently am
still trying to clarify what the gears used are like.

Andrew


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Starhawk
Space Ranger
*****

Reged: 09/16/08

Loc: Tucson, Arizona
Re: Why me? new [Re: OzAndrewJ]
      #5402258 - 09/04/12 01:50 AM

This is horrifying. I thought the NexStar SE was a PITA tracking mount. I was wrong.

-Rich


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neilson
professor emeritus


Reged: 08/22/10

Re: Why me? new [Re: Starhawk]
      #5404255 - 09/05/12 01:52 AM Attachment (25 downloads)

Hi everyone,
I got my Celestron 9.25 Edge ota today. The LX80 expert at OPT that sold me my OTA failed to mention that the Celestron 9.25 would not mount to the LX80. So I called him and he was going to sell me an ADM V2D adapter and I asked him the length of the vixen dovetail that fits into the Meade saddle and he said almost 4". Meade was slick and notched out just over 3 5/8" on the beveled side of the saddle. That leaves around 1/8" on each corner edge. There is no way I am going to risk my new $2,000 ota with that. Just a bump and my ota would be on the ground. So I am forced to remove that nice wide orange dovetail and buy an ADM VC9.25 v series dovetail bar. I emailed ADM and recommended then to start making that dovetail longer to fit the LX80. I also found that on my LXD75 SN10" ota's dovetail its only beveled 3 1/2" so if you put it on and lock it down when it slews your OTA will go flying to the ground. Meade what were you thinking? Did you do this on purpose? They made it so you can't mount their older ota's unless you change out the dovetail. And if you don't notice it beforehand you will loose your ota. Meade you need to recall all your saddles and replace them with saddles that have a beveled slot all the way across, or better yet just update to the industry standard Losmandy style saddle.
Until my dovetail comes in I used the one off my Explore Scientific refractor and fabricated spacers. I am including a picture of the defective LX80 saddle with the notched out beveled side. The only reason I can think of that Meade notched out the beveled edge was so you couldn't mount their old ota's, and so you couldn't use the adapter to convert it for using Celestron ota's. But I did send an Email to ADM recommending him to make the vixen dovetail longer on the V2D converter so it can be used on the LX80. I wish I would of thought to call ADM and asked him to make me a V2D converter with a longer dovetail but I already ordered the other dovetail bar.
neilson


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neilson
professor emeritus


Reged: 08/22/10

Re: Why me? new [Re: neilson]
      #5404285 - 09/05/12 02:56 AM Attachment (29 downloads)

Hi everyone,
I made a temporary dovetail adapter so I could try out my new Celestron 9.25" Edge OTA on my LX80 mount. I did a polar alignment to less than 5deg. from the pole, then an iterative polar alignment. I took 34 images and not one came out. Not even short exposures. I was using a Meade 10"ota before that came with my mount and Meade told me I should be able to image with it. After being told by everyone then finally admitting it myself the mount just cant handle the 30lbs. 10"ota even though its rated for 40lbs in polar. I replaced the 30lbs. ota with a much lighter one. The Celestron 9.25 ota weights only 20lbs. I was very careful to make sure the balance was perfect. All my star images made trails that had the rocking back and forth motion seen in past images. many had the sideways movement like its tracking in DEC also. even the shortest images were bad. This mount can not image unguided successfully regardless of weight in my opinion. This is happening to others also. I also tried with the weight a little heavy in the East and even tried it heavy in the West then back to center balanced was best for me.
I am going to post an image that's 146 seconds long exposure. I cropped it a little and brightened it so you can see the smaller star trail on the left that looks like an upside down "V". Yes this image looks alot like the one I posted before with the 10" ota.
I will see if I can try a guided image tomorrow but it will probably turn out like Kevins guided images. Star trails but mine will be much worse because of the f/10.
Meade needs to get on the ball and fix whats wrong with the tracking. both guided and unguided. I didn't spend all this money on a mount that's polar cant be used for imaging. It's bad enough It can't handle the advertised 40lbs but I spent more money on a lighter ota that's half of the max load rating and it wont work for imaging either. If I cant image with this mount than It's of no use to me. Maybe I will have better luck at guided imaging than Kevin had. At least I will give it a try.
neilson


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OzAndrewJ
scholastic sledgehammer
*****

Reged: 11/30/10

Re: Why me? new [Re: neilson]
      #5404294 - 09/05/12 03:08 AM

Gday Neilson

Just for info, after you did all the iterations etc
what method did you use to do the align,
one star, two star or easy???
Also, rough date/time/location ( nearest city will do )
and target you were pointed at for the shot.
I will simulate it and see what my bench test shows re
commands being sent to the DEC motors.

I have just reconfirmed that if you do a polar one star,
no tracking commands ( that i have seen to date ) are
ever sent to the DEC motor.
If you did a 2 star and got a message that you are
a set distance up/sideways from the pole,
then the DEC motor is 100% getting tracking commands,
but i havent seen any "odd" ones yet.
Maybe after a set amount of movement,
it figures out it isnt on target anymore and resets itself ( in DEC )
That would/may account for the V shape.

If you did do a 2 star align, can you retry using a one star.
If you did do a one star, i'm stumped,
but there are other ways to see whats going on.
If you have my basic peek patch loaded, we can run a log
of the peeked raw encoder positions whilst it is tracking.
If we see a spike on the image, but no encoder movement
in the peeks, its mechanical.


Andrew

Edited by OzAndrewJ (09/05/12 03:40 AM)


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neilson
professor emeritus


Reged: 08/22/10

Re: Why me? new [Re: OzAndrewJ]
      #5404676 - 09/05/12 11:02 AM

Hi Andrew,
I did an easy alignment before and after the iteration polar alignment and it said less than 5deg from pole. The star was Arcturus. My location is latitude 28 58' north, longitude 98 26' west (Pleasanton, Texas U.S. zip code 78064)(nearest large city is San Antonio, Texas) time -06. sept. 4, 2012 10:31pm. On Images before this one I did not sync. but on this one I did. The results were the same. I will try a one star alignment next time. I do not have any patches at this time installed. I will consider it.
I am pleased to know if I do a one star alignment it wont adjust in DEC. it seams that if it did it would help but it doesn't. It would be nice if it would compensate if my polar alignment were off but I tried once before to image with it off the pole but it didn't do well. But maybe it makes good enough corrections for visual. But then there's that thing, why would I use polar for visual when I have Alt/Az. And if I were doing both I would of done iteration for the imaging so it would be accurate for visual.

I decided to check the DEC bearings for grease since the RA bearings were dry. It was tricky trying to figure out how it comes apart but I did. There was a small amount on the outside so I thought they would have grease.
They were dry also. I should have known they might be. I used "Super-Lube" synthetic grease. It is very slick and does not cause drag. I put it together and the bearings lock collar was finger tightened then slightly loosened so it spins super easy with no play in the bearings. I checked amps drawn and both RA and DEC draw 0.34 to 0.35 amps each.

neilson


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Mkofski
Pooh-Bah
*****

Reged: 07/19/11

Loc: Greenfield, Indiana, USA
Re: Why me? new [Re: neilson]
      #5405184 - 09/05/12 04:10 PM

Nelson,

It must be VERY frustrating to spend that much time trying to get the mount to work as advertised! Little consolation for the time and money, but thanks for making the road a bit easier for those of us that are just now getting the mount. After all your problems, I sold my Meade 10" SCT and plan on trying AP with my 80mm refractor to start with and work up from there.


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OzAndrewJ
scholastic sledgehammer
*****

Reged: 11/30/10

Re: Why me? new [Re: neilson]
      #5405409 - 09/05/12 06:42 PM

Gday Neilson

Quote:

I do not have any patches at this time installed. I will consider it.




Let me know if you want to try.
With the peek portion of the patch loaded, we can read the raw encoder offset to the nearest tick, ie about 1/3 of an arcsec.
By letting the scope track, and then logging this data over time,
we can see if there are "real" positional adjusts getting done.

Andrew


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neilson
professor emeritus


Reged: 08/22/10

Re: Why me? new [Re: Mkofski]
      #5405530 - 09/05/12 07:52 PM

Hi Mike,
I'm sorry you had to sell your 10"ota. I didn't like having to get rid of mine. I'm glad to be able to help and I don't really mind doing repairs and adjustments, but after all this it is disappointing that I still cant image. Maybe we'll get it figured out soon, or Meade will come up with a fix. If you have any luck imaging be sure to post it here.
neilson


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Mkofski
Pooh-Bah
*****

Reged: 07/19/11

Loc: Greenfield, Indiana, USA
Re: Why me? new [Re: neilson]
      #5405587 - 09/05/12 08:57 PM

Neilson (not Nelson),

I'm a real newbie so my results, for a while anyway, won't help the cause much. Still waiting on the LX80 anyway.


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OzAndrewJ
scholastic sledgehammer
*****

Reged: 11/30/10

Re: Why me? [Re: neilson]
      #5405676 - 09/05/12 10:15 PM

Gday Neilson

Quote:

I did an easy alignment before and after the iteration polar alignment and it said less than 5deg from pole.




Thats actually 5 arcmin from pole.
Doing a few more tests today, i have confirmed ( so far )
that if you do a polar one star, or a two star and get the "< 5' from pole" message, then the scope doesnt "track" in DEC.
If you get the message that you are a set dist up/dn and sideways from the pole, the DEC motor does track, albeit glacially.
This may trigger backlash, but that still shouldnt have given the V shape plot you seem to be getting.
All very weird.

Andrew


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dmdouglass
professor emeritus


Reged: 12/23/07

Loc: Tempe, AZ
Re: Why me? [Re: OzAndrewJ]
      #5405691 - 09/05/12 10:23 PM

Neilson...

Check on top of page, upper left corner, for PM.


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neilson
professor emeritus


Reged: 08/22/10

Re: Why me? [Re: OzAndrewJ]
      #5405912 - 09/06/12 01:05 AM Attachment (20 downloads)

Hi Andrew,
I wish I would of read this sooner then I would of tried imaging with the alignment slightly off pole with it stating how far off, just to see how it does.
I always get the alignment to say less than 5' from the pole before my iteration alignment.
Today there is gusts of wind, they are light but my RA spring thing still bounces. I am going to tighten it all the way up or find a heavier spring tomorrow. I still did some imaging in between the wind gusts.
First I did the easy and iteration alignments and it said less than 5' from the pole. My images were the same as always with trails in both directions. Then I did a one star alignment. Wow, you are right Andrew. Now my drifts were only in RA. No more inverted "v" trails. But of course I still have star trails. I tried moving the weights west heavy then east heavy but the best results I got were still perfect center balance. I noticed on my bad images the trails look like dots in a row. Not just todays either. I will post my best image tonight of Vega. The image is cropped and only 34 seconds because of the light gusts. It was calm in between gusts.

neilson


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